With help from the C.I.A., Arab governments and Turkey have sharply increased their military aid to Syria’s opposition fighters in recent months, expanding a secret airlift of arms and equipment for the uprising against President Bashar al-Assad, according to air traffic data, interviews with officials in several countries and the accounts of rebel commanders.

The airlift, which began on a small scale in early 2012 and continued intermittently through last fall, expanded into a steady and much heavier flow late last year, the data shows. It has grown to include more than 160 military cargo flights by Jordanian, Saudi and Qatari military-style cargo planes landing at Esenboga Airport near Ankara, and, to a lesser degree, at other Turkish and Jordanian airports.

Read the rest of C.J. Chivers and Eric Shmidt’s report at the NY Times